Stability means for a controller for fluid pressure operated devices

ABSTRACT

An improved, stabilizing means for a controller operatively connected to a servomotor for controlling flow to a fluid pressure device. In a neutral position, a plurality of flow control ports in first and second valve members, one member disposed within the other, are in registry with one another to direct inlet pump flow to an outlet. In an actuated position, the flow control ports are positioned a predetermined degree out of registry as one valve member is rotated relative to the other to thus communicate inlet fluid to the servomotor and metered fluid from the servomotor to the fluid pressure device. The improved stability means dampens the sudden pressure changes within the modulating range as the controller is moved from one position to another. More particularly the stabilizing means comprises an orifice arrangement for augmenting flow which is disposed relative to certain flow control ports in one valve member to control the flow area into flow ports of the second member upon relative movement of the valve members.

United "States Patent [191 Uppal June 25, 1974 STABILITY MEANS FOR A CONTROLLER FOR FLUID PRESSURE OPERATED DEVICES 75 Inventor: Sohan L. Uppal, Hopkins, Minn.

[73] Assignee: Eaton Corporation, Cleveland, Ohio [22] Filed: Oct. 24, 1972 [21] Appl. No.: 300,037

[52] US. Cl....... 418/61 B, 180/792 R, 137/625.24

Primary Examiner-Carlton R. Croyle Assistant Examiner-John J. Vrablik Attorney, Agent, or Firm :Teagno & Toddy [5 7] ABSTRACT An improved, stabilizing means for a controller operatively connected to a servomotor for controlling flow to a fluid pressure device. In a neutral position, a plurality of flow control ports in first and second valve members, one member disposed within the other, are in registry with one another to direct inlet pump flow to an outlet. In an actuated position, the flow control ports are positioned a predetermined degree out of registry as one valve member is rotated relative to the other to thus communicate inlet fluid to the servomotor and metered fluid from the servomotor to the fluid pressure device.

The improved stability means dampens the sudden pressure changes within the modulating range as the controller is moved from one position to another. More particularly the stabilizing means comprises an orifice arrangement for augmenting ilow which is disposed relative to certain flow control ports in one valve member to control the flow area into flow ports of the second member upon relative movement of the valve members.

14 Claims, l6-Drawing Figures PAIENTEDauuzs 1914 SHEET 1 0F 5 FIG. I

FIG. 2

STABILITY MEANS FOR A CONTROLLER FOR FLUID PRESSURE OPERATED DEVICES This invention relates to a controller for fluid pressure operated devices and more particularly to an arrangement for stabilizing the fluid flow therethrough.

The invention is particularly applicable to a controller-gerotor application for use with a power-steeringthe invention has applicability to any type of modulating valve arrangement for actuating a fluidic device by supplying pressure thereto.

A power-steering control of the type to which this invention pertains is described in U.S. Reissue Pat. No. 25,126 to L. L. Charlson, reissued Feb. 20, 1962 and assigned to the present assignee. The Charlson patent discloses a modulating valve unit or controller feeding pressure into and out of a servomotor of the gerotor type. The controller disclosedcomprises a controller body to which is secured a pump inlet, a reservoir outlet and two conduits, inlet and outlet, feeding to a power-steering cylinder. The vehicle steering wheel is directly connected to the controller and when the steering wheel is in a neutral position, defined as any nonrotating or stationary position, fluid is supplied from the pump inlet, through the-controller to the reservoir out let. When the steering wheel is rotated fluid pressure travels from the pump inlet through the gerotor arrangement where it is metered and transmitted through one conduit leading into the power-steering cylinder. This causes the piston to travel displacing fluid into the other conduit and back through the controller to the reservoir outlet. If the steering wheel is rotated in the opposite direction, the pressure into and out of the aforementioned conduits is reversed to effect opposite movement of the cylinders piston.

More particularly, Charlson achieves this control of fluid direction by employing a modulating valve body in working communication with a gerotor servomotor comprising a fixed ring member receiving a rotating and orbiting star-member. The valve body comprises a housing containing the inlet, outlet and cylinder lines along with valving passages communicating with the gerotor. Disposed within the housing is a rotatable, hollow cylindrical sleeve member, having various passages, recesses, chambers, etc. adapted to be in communication with the various lines in the instances described above. Disposed within the sleeve member is a rotatable, hollow, cylindrical spool member also having various chambers, passages, etc. whereby fluid is communicated through the aforementioned passages in the sleeve member.

The spool is fixed to the steering wheel and also coupled to the sleeve by a pin and set of springs in a manner which permits a predetermined degree of relative movement between the sleeve and spool before the spool and sleeve are commonly rotated thereby. Also extending within the spool is a dogshaft, splined at one end to the star member and bifurcated atthe other end to receive the pin; the dogshaft thus rotates the pin in direct proportion to the star members rotation.

In the neutral positiomfluid pressure is fed into the pump inlet through a plurality of circumferentially spaced, relatively small apertures in the sleeve which are aligned with a like member of similarly sized apertures in the spool; the apertures in both spool and sleeve being longitudinally located in line with the pump inlet. The fluid then travels through the hollow in the spool and out the spool and sleeve by other communicating passages to the outlet reservoir.

When the steering wheel is slightly rotated from neutral the apertures begin to move out of registry with one another. Simultaneously, other passages begin to move into communication with one another. The inlet pressure fed into the other passages increases as the passages move further into registry until the pressure in the servomotor reaches a force level sufficient to overcome the resistance of the steering arrangement and steering occurs. When the wheels rotation is stopped, and steering wheel is released, centering means return the spool and sleeve members to a relative neutral position.

As thus defined, Charlsons device did not provide enough modulating range between sleeve and spool or neutral band width necessary to give the driver the best possible control of the steering arrangement. This resulted from the particular aperture arrangement in the spool and sleeve which caused these apertures to move out of registry with one another upon relatively slight movement of the wheel from neutral. When this occurs, the rapid pressure change within the controller may cause oscillation between spool and sleeve, in turn causing vibration to be felt in the steering wheel. Also, in Charlsons device the spool is not pressure balanced which may cause binding of the sleeve on the spool under higher pressures, unless the diametral clearance between spool and sleeve is increased causing unwanted leakage and slip.

Attempts were made to improve the Charlson device. In particular, gain characteristics were changed by employing a row of relatively large circumferentially spaced apertures removed a slight axial distance from a row of smaller, similarly aligned apertures in both spool and sleeve members. The smaller apertures moved out of contact with one another at a smaller rotational angle than the larger ones. This provided an initially large area to give a neutral band resulting in small pressure change over a nominal angular rotation which then instantaneously changed to maximum pressure over a very small rotation of sleeve with respect to spool, which in turn set up vibrations in the spool as it oscillated between the limits of valve modulation when the steering arrangement was rotated from or to neutral position.

It is thus a principal object of 'the subject invention to provide a controller for a fluid pressure device which possesses improved stability characteristics.

In accordance with the invention there is provided a fluidic device coupled to a modulating valve arrangement comprising a controller and servomotor which functions in a manner similar to that of the aforedescribed Charlson device. Thus the controller comprises a stationary outer casing having at least a pump inlet and an outlet, either closed or open to a reservoir, and also interchangeable inlet and outlet lines to a cylinder. Received in the casing is a hollow, clindrical, rotatable sleeve member. A hollow cylindrical spool member having one end fixed to the steering wheel is disposed within the sleeve member.- A pin and slot arrangement between the spool and sleeve limits maximum movement of the spool and sleeve relative to one another. A set of leaf springs between sleeve and spool provides means for returning the spool and sleeve back to a neutral position when steering wheel is released. Means are provided for driving the sleeve in direct relation to the output of the servomotor.

At the pump inlet side and in communication therewith the sleeve member has at least one row of circumferentially spaced first apertures. Circumferentially aligned with and longitudinally spaced on one side of the first apertures is at least one row of smaller-sized second apertures. A plurality of flow augmentation orifices of predetermined geometric configuration are longitudinally positioned and circumferentially spaced with respect to the second apertures so that an orifice is positioned in predetermined circumferential distance on each side of each of said second apertures.

The spool member has a number of axially extending configured slots therethrough; the number and position corresponding to and circumferentially aligned with the first and second apertures. As the sleeve and spool rotate relative one another past the point where the second apertures have moved out of contact with the slot, either the upper or lower orifices will move into contact with each slot thus providing an additionally increasing area which prevents the pressure change from building to an instantaneous maximum.

It is thus an object of the invention to provide novel means to obtain a gradual pressure build-up in a controller for operating a fluid device.

It is another object of the invention to provide in a controller for a fluid pressure device, novel means for preventing instantaneous pressure changes as the controller moves from a neutral to an actuated position.

A still further object of the invention is to provide a relationship between the resistance to flow from feed to cylinder and return from the cylinder to reduce the possibility of cavitation in the system.

Yet another object is to provide in a controller for a fluid pressure device having a spool valve member and a sleeve valve member, pressurizing means to maintain the spool and sleeve members in neutral or centrally disposed relation and to minimize distortion of the sleeve to prevent binding between said spool and sleeve.

The invention may take physical form in certain parts and arrangement of parts a preferred embodiment of which will be described in detail herein and illustrated in the accompanying drawings hereof and wherein:

FIG. 1 is a diagram showing the controller used in the power steering system of a vehicle;

FIG. 2 is an enlarged view partly in elevation and partly in axial section taken substantially along line 22 of FIG. 1, some parts being broken away;

FIG. 3 is an axial, sectional view taken substantially on the Line 33 of FIG. 2;

FIG. 4 is a transverse sectional view taken substantially along line 44 of FIG. 3, some parts being broken away;

FIG. 5 is a fragmentary view in side elevation of one of the valve elements in the controller;

FIG. 6 is a fragmentary view in side elevation of another valve element in the controller;

FIGS. 7-12 are views in transverse sections taken respectively along lines 7-7, 8-8, 99, 10-10, lIl1,12-12 of FIG. 3;

FIG. 13 is a graph of valve deflection versus pressure change; and

FIGS. l4, l5, and 16 are overlaying views of apertures and orifices in valve elements at various valve deflections.

Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only and not for the purpose of limiting same, there is provided a controller A operatively connected to a servomotor B for controlling a power-steering arrangement C. Controller A comprises a primary valve, hereafter referred to as spool member 10 disposed within a follow-up valve hereafter referred to as a sheeve member 12 which in turn is disposed within a tubular casing 14. Stabilizing means D is provided for controller A which comprises a plurality of orifices 16 in geometric arrangement with a plurality of apertures 20 in sleeve member 12 coordinating with a plurality of slots 18 in spool member 10.

Referring now to FIG. 1 the tubular casing 14 of controller A is shown as having a pump inlet 22 which is connected by means of a conduit 23 to a source of fluid pressure such as a pump 24 which in turn is connected to a reservoir of tank 25 by a conduit 26. Tubular casing 14 is also provided with a reservoir outlet 28 for return of fluid to reservoir 25 by means of conduit 29. Tubular casing 14 is also provided with a pair of interchangeable cylinder inlets and outlets 31, 32 with respective conduits 33, 34 leading to opposite ends of a power-steering cylinder 35 having mounted for axial reciprocatory movement therein a piston equipped plunger rod 36. The plunger rod 36 is connected to the steering linkage 38 of a vehicle, not shown, by means of the usual bell crank 39 and rigid link 40 whereby the vehicle wheels 41 are steered in the usual manner.

SERVOMOTOR Referring now to FIGS. 2, 3, and 7, there is shown a servomotor B of the gerotor type although it should be appreciated that any type of servomotor such as a vane type may be employed therefore. The gerotor illustrated comprises the usual internally toothed ring member 44 which is fixed receiving an externally toothed star member 45 which is free to rotate and orbit about its axis. Ring and star members 44, 45 are so arranged that their teeth 46, 47 respectively move into and out of interrneshing engagement and define expanding and contracting fluid chambers 48 during rotary and orbital movement of ring member 44. The construction and operation of ring and star members 44, 45 is similar to that shown and described in US Letters Pat. No. 2,821,171. Briefly, by introducing fluid under pressure to some of the chambers 48 and permitting fluid to escape from other chambers, the externally toothed star member 45 partakes of an orbital movement about the axis of the internally toothed ring member 44 rotating one tooth spacing for every orbit thereof. Inasmuch as there are seven ring teeth 46 and six star teeth 47 thus defining seven pressure chambers 48, the star member 45 will rotate once on its own axis during six cycles of orbital movement thereof about the axis of the internally tooth ring member 44.

The servomotor arrangement B also comprises an end plate 52 abutting an axial end face 53 of star and ring members 45, 44 along with a bearing plate 54 abutting the opposite axial end face 55 of ring and star members 44, 45; bearing plate 54 being intermediate the controller assembly and servomotor arrangement A, B. Bearing plate 54 has a centrally disposed opening 56 for receiving the shaft portion 57 of a dogshaft or drive shaft 58 having a crowned splined head 59 in driving engagement with a splined'central opening 60 in star member 45. Bearing plate 54 is also shown as having seven valving ports 63 adapted to be in communication with pressure chambers 48 in a manner known to those skilled in the art. The servomotor arrangement B thus described is secured to the tubular casing 14 of controller A by bolts 64 extending through the end plate 52, ring member 44 and bearing plate 54 to engage suitably threaded openings in tubular casing 14. Servomotor arrangement B is provided with suitable seals 66 to prevent leakage therefrom.

CONTROLLER The controller assembly comprisesa tubular casing 14 having a substantially cylindrical opening 70 extending therethrough into which is disposed a hollow cylindrical sleeve member 12 which in turn receives a hollow cylindrical spool member 10.

Tubular casing 14 has a pumy inlet port 72, a reservoir outlet port 73, interchangeable inlet and outlet ports 74, communicating respectively with a pump inlet groove 76, an outlet reservoir groove 77, interchangeable inlet and outlet cylinder grooves 78, 79;

each groove opening to the cylindrical opening 70. Also seven L-shaped valving passages 81 are circumferentially spaced in tubular casing each valving passage 81 having one end 82 adapted to communicate with a valving port 63 in the bearing plate 54 and its other end 83 opening to the cylindrical opening 70 in tubular casing 14. A plurality of circumferentially spaced threaded holes 85 are shown drilled in one axial end face 86 of tubular casing 14 to secure controller A to a mounting bracket 87 as shown in FIG. 1 by means of machine screws and the like. I

Rotatably disposed within the cylindrical opening 70 in tubular casing 14 and in close engagement with the walls of the opening is sleeve member 12. Sleeve member 12 has one axial end 89 abutting bearing plate 54 with its other axial end 90 abutting an end cap88. End cap 88 is shouldered and received in a similarly stepped recess 91 in tubular casing 14 and secured in this position by a snap ring 92 or the like. Nestingly received within the sleeve 12 and concentric therewith its spool member 10 which is hollowed for the greater part of its length to thereby define an axial recess or passage 94. One axial end 96 of spool 10 is in substantially abutting engagement with bearing plate 54 with its opposite end 97 abuttingly engaging thrust bearing 98 mounted within the shouldered portion of end cap 88. Seals 99, 100 between tubular casing 14 and end cap 88 and end cap 88 and spool 10 respectively seal the controller arrangement A.

Referring now to FIGS. 2, 3, and 4, axial end 97 of spool 10 is shown splined for connection to the shaft of the steering wheel 42. Spool 10 is coupled to sleeve 12 for limited rotary movement with respect to sleeve 12 and also for common rotary movement with sleeve 12 by means of a transverse drive pin 102. More particularly transverse drive pin 102 extends radially through a pair of diametrically opposed circumferentially extended slots 103 in spool 10 and the opposite ends of drive pin posed openings 104 in sleeve member 12. Thus when 102 are snugly received in diametrically op-' spool member 10 isrotated by steering wheel 42 from its centered or neutral position, drive pin 102 and correspondingly sleeve 12 will be engaged only after some limited rotational angle of the steering wheel has been exceeded, which for the purposes of explanation will be established as l0". It should also be noted that the central portion of drive pin 102 receives a bifurcated end portion 61 of dogshaft 58. Thus rotation of star member 45 causes similar rotation of drive pin 102. Finally there is provided a plurality of resilient leaf springs 106 which extend radially through aligned diametrically opposed'notches 107, 108 in the spool and sleeve 10, 12 for yieldingly urging spool 10 and sleeve 12 to the neutral position relative to each other.

Referring now in detail to the spool member 10 as shown in FIG. 5, a plurality of configured slots 18 are longitudinally located at the bearing plate axial end portion 96 of spool 10 and adapted to be in communication with pump inlet groove 76. Slots 18 form part of stabilizer means D and will be referred to in detail hereafter. It should suffice to state at this time that slots 18 are adapted to be in communication with pump inlet 22 when the spool and sleeve 10, 12 are in neutral position and some degree out of communication with pump inlet 22 when the controller A is actuated by rotatably displacing spool 10 relative to sleeve 12. Longitudinally spaced from slots 18 and-adapted to be in constant communication with pump inlet groove 76 is an external peripheral feed groove 1 10. In communication with feed groove 110 and longitudinally extending along spool 12 to a point not beyond the valving passage openings 83 are six circumferentially spaced discontinuous valving slots 112. interspersed and circumferentially spaced between valvingshots 112 are six feed slots 114 adapted to be employed in right or left turns. Each feed slot 114 extends longitudinally from the valving passage openings 83 past one cylinder groove 78 and temiinates at a point just beyond the other cylinder groove 79 in tubular casing 14. Circumferentially spaced between feed slots 114 and spaced in line with and longitudinally extending a distance equal that of one cylinder groove 78 are six first return slots 116 communicating with axial passage 94 in spool 10 which are shallow to give resistance to the return flow from the cylinder to reduce cavitation. Also circumferentially spaced between feed slots 114 and spaced in line with and longitudinally extending a distance from the second cylinder groove 79 to the outlet reservoir groove 77 in tubular casing 14 are four second return slots 118 opening to passage94 in spool 10 which are deep to have the same area as the six 116 shallow slots. Finally, interposed between second return slots 118 and aligned with the outlet reservoir groove 77 are four outlet holes 120 circumferentially spaced from diametrically opposed leaf spring notches 107. Outlet holes 120 extend through spool 10 and are adapted to be in communication with passage 94. The two slots 160, 162 communicating with the pin slot of spool 10 are for uniform circumferential pressure balance of the spool. It should be noted that the return slots were discontinued in two steps 116 and 118 to connect the feed slots 114 for pressure balancing and for collector function. It should also be noted that a first pressure balancing groove 122 peripherally extending around the exterior surface of spool 10 is longitudinally aligned between the inlet and outlet cylinder grooves 78, 79. Also a second pressure balancing groove 124 extending peripherally around the exterior surface of spool member 10 is longitudinally aligned between one cylinder groove 78 and valving passage opening 83 for purposes which will hereafter be explained.

Referring now in detail to sleeve member 12 as shown in FIG. 6, a plurality of apertures 20 and orifices 16 are longitudinally located at the bearing plate axial end portion 89 of the sleeve and are adapted to be in communication with pump inlet groove 76. Apertures 20 and orifices 16 form part of stabilizing means D and will be referred to in detail hereafter, it being sufficient to state that the apertures 20 and slots 18 in spool 10 align with one another to provide a fluid flow path when controller A is in a neutral position and are displaced relative to one another to close off the fluid flow path as controller A is actuated. Longitudinally spaced from apertures 20 and'axially aligned with peripheral feed groove 110 in spool 10 and adapted to be in communication with pump inlet 76 are 12 circumferentially spaced feed apertures 111. Longitudinally spaced from feed apertures 111 and aligned with valving passage openings 83 are 12 circumferentially spaced valving apertures 113. Valving apertures 113 are axially aligned with valving and feed slots 1 12 and 114 in spool 12. Thus some of the valving apertures 1 13 in sleeve 12 communicate pump inlet pressure from valving shots 112 via valving passages 81 to half the pressure chambers 48 in servomotor B which are at high pressure while the other pressure chambers 48 at low pressure are communicated to feed slots 114 in spool 10 via other valving apertures 113 in sleeve 12 in a sequential manner known to those skilled in the art.

Longitudinally spaced from valving apertures 113 and aligned with one of the cylinder grooves 78 in tubular casing 14 are six circumferentially spaced first return apertures 117. First return apertures 117 are axially aligned with first return slots 116 in spool 10. Longitudinally spaced from first return apertures 117 and in alignment with the other cylinder line groove 78 in tubular casing 14 are six circumferentially spaced second return apertures 119. Second return apertures 119 are axially aligned with second return slots 118 in spool 10. As best shown in FIGS. 10 and 11 apertures 117 and 119 are circumferentially spaced relative one another in such a manner that when return apertures 117 are in communication with return slots 116, the second return apertures 119 are out of communication with second return slots 118 and vice-versa. Longitudinally spaced from additional return apertures 119 and aligned with outlet reservoir groove 77 are ten outlet apertures 121 circumferentially spaced around the diametrically opposed leaf spring notches 108. Outlet apertures 121 are axially aligned with outlet holes 120 in spool 10. Apertures 20, 111, 113, 117, 119, and 121 extend through sleeve 12.

STABILIZING MEANS Stabilizing means D comprises the slots 18 in spool 10 and orifices 16 and apertures 20 in sleeve 12 and more particularly the geometric configuration and relationship therebetween.

Referring now'to FIGS. 6, 8, 14, 15, and 16 there is shown a particular configuration of apertures 20 in sleeve membervl2. More particularly four elongated, relatively large charging apertures 128 are circumferentially spaced around sleeve member 12. Circumferentially spaced between charging apertures 128 is a first row 130 of eight circular apertures 132 of a given diameter J. Longitudinally spaced towards the bearing plate axial end 54 of sleeve 12 is a second row 134 of circumferentially spaced circular apertures 132; the apertures in the second row 134 axially align with the apertures in the first row 130. Longitudinally spaced on the other side of the first row 130 of circular apertures 132 are eight similarly circumferentially spaced gain holes 136 of a given diameter K arranged in a third row 138', each gain hole 136 in the third row 138 axially aligned with corresponding apertures 132 in the first and second rows 130, 134. Longitudinally spaced from the third row 138 of gain holes is a fourth row 140 of gain holes 136 likewise circumferentially spaced so that each gain hole 136 in the fourth row 140 is axially aligned with a corresponding gain hole in a third row 138 and aperture in the first and second rows 130, 134. Disposed above and below each gain hole 136 is the third and fourth row 138, 140 at a predetermined centerline distance L is an augmenting orifice 16; there thus being 16 orifices in the third row 138 and 16 orifices in the fourth row 140 with each orifice in the third row axially aligned with an orifice in the fourth row. In the embodiment illustrated the gain holes 136 have diameters approximately half of the circular apertures 132 and the diameter of orifices 16 are equal to that of gain holes 136. The centerline spacing L between each pair of axially aligned augmenting orifices 16 and each pair of axially aligned gain holes 136 in the third and fourth rows respectively 138, 140 is equal to an are extending 6% of the periphery of sleeve 12 in the embodiment shown.

Referring to FIGS. 5, 8, 14, 15, and 16 there is shown a plurality of slots 18 in a particular arrangement on spool member 10. In particular there is provided four circumferentially spaced charging slots 129 adapted to be in alignment with charging apertures 128 in sleeve 12 when controller A is in a neutral position. Circumferentially spaced so as to be on each side of each charging slot 129 are 12 discontinuous pressure slots 131 which do not extend through spool 10. Circumferentially spaced and interspersed between charging slots 129 are eight stability slots 133 adapted to be in communication with circular apertures 132 and gain holes 136 when the controller is in a neutral position. In particular each stability slot has a width at its bearing plate axial end which is equal to that of diameter J of circular apertures 132 in sleeve 12. At the opposing axial stability slot end 137, stability slot 133 has a width equal to diameter K of the gain holes 136 in sleeve 12.

OPERATION As thus described with the steering wheel 42 in a neutral position, defined hereinbefore as any non-rotating or stationary position, fluid leaves pump 24 under pressure and travels into the pump inlet port 72 and from thence into the pump inlet groove 76 in tubular casing 14. From pump inlet groove 76 the fluid travels through the feed apertures 111, the charging apertures 128, the circular apertures 132, gain holes 136 and augmented orifices 16 in sleeve member 12. The fluid from the feed apertures 111 in sleeve 12 thence travels into the peripheral feed groove 110 in spool 10 and enters the discontinuous valving slots 112 whereupon the flow is dead ended as valving slots 112 are not communicated with any other passages at this time. Similarly the fluid pressure in augmented orifices 16 is dead ended as the orifices are not in communication with any other slots or passages. Thus the fluid flows from the charging apertures 128, circular apertures 132, and

degree out of registry with the apertures 20 in the sleeve 12 and the valving slots 112 and feed slots 114 have correspondingly moved into registry with valving apertures 1 13 in sleeve 12. Pump pressure is thus communicated from valving slots 112 through the apertures 1 13 into the servomotor B and returned from the servomotor through other valving apertures 113 into feed slots 114. If the steering wheel is rotated to the right the first return apertures 117 in sleeve 12 will be in communication with feed slots 114 while the second return apertures 119 in sleeve 12 will be in communication with the second return slots 118 in spool 10. Thus the metered fluid in feed slot 114 will travel through the interchangeable inlet cylinder grooves and port 78, 74 in tubular casing 14 to power steering cylinder 35. Actuation of cylinder 35 will displace fluid into interchangeable outlet cylinder port and groove 75, 79 through.

second return apertures and slots 119, 118 in sleeve and spool member 12, through spool passage 94 and into reservoir 25 via outlet holes and apertures 120, 121 in the spool and sleeve. When the steering wheel is rotated to the left the metered fluid in feed slots 114 communicates with second return apertures 119 in sleeve 12 to transmit the metered fluid through interchangeable outlet cylinder groove and port 79, 75 to the power-steering cylinder 35. Fluid displaced from power-steering cylinder 35 returns to controller A in sleeve 12. Thus valving passages 81 in tubular casing 14 will increase in pressure as valving slots 112 move into greater registry with valving apertures 113 as steering wheel 42 is moved beyond X When the pressure thus communicated into gerotor chambers 48 slightly exceeds the pressure required to move the piston in power-steering cylinder 35 the controller A is actuated. It should be noted that maximum communication between feed slots 112 and valving slots 114 with valving apertures 113 in the embodiment shown is established at 10 which is the angle that drive pin 102 is engaged by the circumferentially extended slot 103 in spool 10.

Assuming a steady rotation of the steering wheel 42 at any speed, it should be clear from the foregoing that when Y of rotation is exceeded (Y being less than 10) the controller A will be actuated to thus rotate and orbit the star member in servomotor B. As the star member 45 rotates, the dogshaft 58 correspondingly rotates and drives pin 102. Thus the sleeve 12 via the pin 102 instantaneously follows up the spool s rotation. Continuous rotation of spool 10 via steering wheel 42 results in continuous follow-up rotation of sleeve member 12. Thus the Y of relative rotation between the ring and spool will remain effectively constant for a constant steering wheel speed. When the steering wheels rotation is stopped, the dogshafts rotation will move the sleeve position relative to the spool to an angular displacement less than Y and the leaf springs 106 will tend to return the spool and sleeve members into a centered neutral position. The degree of rotation of sleeve relative to spool is also a function of rate of steering wheel speed. The relative rotational degree (Y increasing as steering wheel speed increases because servomotor B is a positive displacement mechanism which displacesa constant metered volume of fluid per revolution.

through interchangeable cylinder inlet port and groove 74, 78 in communication with return aperturesand slots 117, 116 in sleeve and spool members 12, 10. The fluid then travels through passage 94 and spool 10 exiting to the reservoir 25 via the outlet holes and apertures 120, 121 in spool and sleeve members l2, 10.

It should be additionally noted that when the controller A is actuated spool 10 is centered within sleeve 12 by the first and second pressure balancing grooves 122,124 in spool member 10 which receives pressure from feed slots 114. The spool is additionally balanced at its bearing plate axial end 96 by means of the charging apertures 128 in sleeve 12 communicating with pressure slots 131 in spool 10. Thus the spool is prevented from being displaced within the sleeve and/or the sleeve is prevented from collapsing, thereby avoiding binding between the two membersduring operation. Additionally any axially rocking or cocking of the spool which contributes to binding of the spool is avoided. 1

Now with particular emphasis on the action of controller A as it moves from neutral to actuated position or vice-versa, it should be apparent thatwhen steering wheel 42 is slightly rotated X slots 18 in spool 10 will move X out of registry with the apertures 20 in sleeve 12. Similarly valving and feed slots 112,114 in spool 10 will move X into registry with valving apertures 113 The ratio of change in flow resistance to the change in relative rotation determines the sensitivity and stability of the system, and this ratio specifies the gain rate of the controller. Generally if the controller has a linear gain within the working rotational range, it will approach a stable valve. If not, the gain will fluctuate between maxima and minima in a short interval of rotation, causing instability in the valve.

The arrangement of slots, orifices, and apertures 18,16,20 described above and shown in interacting geometric relationship in FIGS. 14, 15, and 16 and in graphical relationship in FIG. 13 provides better working rotational range than prior art devices which prevents the instantaneous pressure changes in the controller as controller A switches from neutral to actuated position.

In particular FIG. 14 shows the alignment of slots, orifices, and apertures 18,16,20 with controller A in neutral position. In this position the total flow area A-1 communicating pressure from the pump inlet groove 76 through to passage 94 in spool 10 comprises the area A-1 of charging apertures 128 plus the area A2 of circular apertures 132 plus the area A-3 of gain holes 136. Also in the embodiment illustrated, the total area of all augmented orifices 16 on one side of gain holes 136 is equal to the area A-3 of gain holes 136. As shown in FIG. 14 augmented orifices 16 are not in communication with stability slots 133 in spool member 10. It should also be noted that relatively large charging apertures 128 and slots 129 in spool and sleeve members 10,12 are provided to permit relatively unimpeded flow through axial passage 94 in spool in neutral position.

When spool and sleeve members 10,12 are slightly rotated relative to each other, gain holes 136 move out of registry with stability slots 133 at a faster rate than do circular apertures 128. Also circular apertures 132 move out of register with stability slots 133 at a faster rate than do charging apertures and slots 128,129. As shown in FIG. at 3 relative movement, gain holes 136 have moved substantially out of registry with stabilizing slots 133, the circular apertures 132 have moved out of registry with stability slots 133 by approximately half of their area while charging aperture 128 have moved proportionately less out of engagement with charging slots 129. Also the spacing L between axial pairs of augmenting orifices 16 and gain holes 136 is such that the orifices 16 have not moved into substantial engagement with stability slots 133 at this point. This condition makes the controller capable of steering the system. It should also be noted that area A-3 of gain holes 136 is so established that if the gain holes 136 were eliminated the flow area in neutral position as illustrated in FIG. 13 would be less, causing higher pressure drop.

As the spool and sleeve continue relative rotation the augmented orifices 16 disposed on one side of gain holes 136 come into registry with stability slots 133 as circular apertures 132 move further out of registry; the areas of orifices 16 and remaining areas of apertures 132 being such that the decreasing areas of apertures 132 is substantially compensated by the augmenting orifices 16. (See FIG. 15.) During this time the charging apertures 128 continue to move further out of contact with charging slots 129, with the total area decreasing but at a less rate than would occur if the augmenting orifices 16 were not present. This is illustrated in the graph shown in FIG. 13 of pressure change versus spool and sleeve deflection. The dotted line 148 shown therein is the pressure change curve which would result if the augmenting orifices 16 were deleted from the controller while the solid line 150 shows a pressure change graph of the controller with augmenting orifices As noted previously, a rotation of Y will produce a controller actuation point which will occur in the arrangement illustrated between 4 and 7 of relative movement between sleeve and spool members 10,12. Thus if it is assumed for purposes of comparison that 5 relative movement produced actuation, a controller with the invention would have a pressure change onethird as severe as a controller without the augmenting orifices 16. Also from FIG. 13 it is clear that the augmenting orifices tend to yield a better approximation to linearity over a wider range of valve deflection. Thus the gain rate of the valve is appreciably gradual when compared to a valve without augmenting orifices and hence the invention will lead to a comparatively stable valve without effecting the total rotation between sleeve and spool which is approximately 10 in the aforesaid valve.

As thus described, it is apparent that improved results would probably occur if each pair of axially aligned orifices 16 above and below each pair of axially aligned gain holes 136 were slotted or if once slotted the orifices would have their widths elongated in a direction away from gain holes 136. Such variations,

however, are difficult to accurately machine in sleeve 12. Also the same effect would be produced if the augmenting orifices or slots 16 were placed on both sides of stability slots 133 in spool 10 and eliminated from sleeve 12.

The invention has been described with reference to a preferred embodiment. Obviously, modifications and alterations will occur to others, upon reading and understanding the specification. It is my intention to include all such modifications and alterations insofar as they come within the scope of the present invention.

It is thus the essence of my invention to provide in a controller having one member movable with respect to another to open and close flow therethrough, an augmenting orifice arrangement which helps in stabilizing the flow when the controller is actuated.

Having thus described my invention, 1 claim:

1. A controller operatively connected to a servomotor for actuating a fluid pressure operated device, said controller comprising valve structure including a primary movable valve element and a cooperating movable follow-up valve element; means for connecting said primary valve element to a control element for common movements therewith; said fluid servomotor including a rotary member coupled to said follow-up element for imparting follow-up movements thereto responsive to rotation of said rotary member; said valve structure defining, an inlet for connection to a source of fluid under pressure and an outlet for return of fluid to said source, a pair of fluid ports for connection to a fluid pressure operated device, and fluid passages communicating with said servomotor; said valve elements each having valve passages which cooperate to direct flow of fluid from said inlet through said servomotor to one of said ports and to direct flow of fluid from the other of said ports to said outlet responsive to movement of said primary valve element in one direction away from a neutral position relative to said follow-up valve element; movement of said primary valve element in the opposite direction from said neutral position causing said valve element passages to be disposed to direct flow of fluid from said inlet through said servomotor to the other of said ports and to direct flow of fluid from said one of the ports to said outlet; the improvement comprising:

said follow-up valve element having at least a first row of a plurality of circumferentially spaced apertures and at least a second row of circumferentially spaced orifices longitudinally displaced from said first row, said orifices circumferentially oriented with respect to said apertures so that one orifice is disposed above and below each first aperture a predetermined distance, and said primary valve element having a plurality of circumferentially spaced slots of number equal to said apertures, each slot axially extending a distance at least equal to the distance from said first row to said second row, said apertures and said slots in communication with one another when said controller is unactuated.

2. A modulating controller for controlling fluid flow to a fluid pressure operated device, said controller comprising:

a casing having a cavity therein, an inlet extending into said cavity and first and second outlets extending from said cavity;

first and second valve members disposed in said cavity, said first and second valve members being relatively movable between a neutral and an actuated position;

said first and second valve members defining a first flow area through said valve members for providing a fluid flow path between said inlet and said first outlet when said valve members are in said neutral position;

said first and second members defining a second fluid flow area through said valve members for providing a second fluid flow path between said inlet and said second outlet when said valve members are in said actuated position, said first flow area being decreased a predetermined amount in said actuated position; and

a third flow area through said valve members, said third flow area being effective to modify the effective area of said first flow area during relative movement of said members between said neutral and actuated positions,

said first and second valve members being sleeve and spool members respectively;

said sleeve member having a plurality of first apertures circumferentially spaced thereabout, said spool member having a like plurality of circumferentially spaced slots extending therethrough;

said first apertures being aligned with said slots to define first flow area, said apertures being movable out of registry with said slots to define said decreased first flow area; and 7 said third flow area being defined by a plurality of second aperatures in said sleeve member, said second aperatures being spaced circumferentially about said sleeve member a predetermined distance on each side of at least some of said first apertures;

said first apertures including a first plurality of generally circular apertures and a second plurality of larger charging apertures interspersed among said circular apertures, and said second apertures including a plurality of augmenting orifices; and

said slots including a pluralityof longitudinally extending slots equal in number to said first plurality and having a width at one end approximately equal to the size of said augmenting orifices and a width at the other end approximately equal to the size of said first apertures and a plurality of charging slots equal in number to said second plurality and having a width approximately equal to that of said charging apertures.

3. A controller operatively connected to a servomotor for actuating a fluid pressure. device comprising:

a casing having an opening therein and at least an inlet and outlet vport communicating with said opening; 7

a'hollow sleeve member rotatably disposed within said opening;

a hollow spool member rotatably disposed within said sleeve member;-

passage means in said sleeve and spool member to direct fluid into said servomotor when said controller is actuated;

control means in said spool and sleeve members to direct fluid pressure from said inlet through said spool to said outlet when said controller is in a neutral position andto change fluid pressure direction through said spool member when said controller is actuated;

said control means further including said sleeve member having at least a first row of a plurality of circumferentially spaced first apertures and at least a second row of circumferentially spaced orifices longitudinally displaced from said first row, said orifices circumferentially orientated with respect to said apertures so that an orifice is disposed above and below each first aperture a predetermined distance, and said spool member having a plurality of circumferentially spaced slots of a number equal to said first apertures and in circumferentially aligned relationship with said first apertures, each of said slots axially extending a distance at least equal to the distance from said first row to said second row, said first apertures and slots in alignment with one another when said controller is in a neutral position. 4. A controller as defined in claim 3 wherein said pre determined distance is sufiicient to communicate an increasing area of said orifices with said slots after said first apertures have rotated a portion of their area out of communication with said slots as said spool and valve members rotate relative to each other.

5. A controller as defined in claim 4 wherein said portion of said first apertures rotated out of communication with said first slots is approximately one-half the area of said first apertures before said increasing area of said orifices begins to compensate for loss of additional area of said first apertures as said first apertures continue to move out of communication with said slots.

6. A controller as defined in claim 3 wherein said passage means includes at least first and second axially spaced peripheral pressure balancing grooves in the exterior surface of said spool member for receiving pressure when said controller is actuated to maintain said spool member centered within said sleeve member.

7. A controller as defined in claim 6 further including a plurality of axially-extending, discontinuous grooves in the exterior surface of said spool member interspersed between said first slots and in at least partial communication with at least some of said first apertures when said controller is actuated.

8. A controller as defined in claim '3 wherein said sleeve member has a plurality of gain holes interspersed between said orifices and circumferentially spaced and orientated to be axially aligned with said first apertures.

9. A controller as defined in claim 8 wherein each gain hole and each orifice have substantially equal areas.

10. A controller as defined in claim 9 wherein said sleeve member has a third row of first apertures of like number of said apertures in said first row, said apertures in said third row circumferentially orientated with respect to said first apertures in said first row to be axially aligned therewith, said third row longitudinally spaced from said first row in a direction away from said second row of orifices, and said first slots in said spool member extending to said third row.

11. A controller as defined in claim 10 wherein said sleeve member has a fourth row of said orifices and said gain holes circumferentially spaced and aligned so that each orifice and gain hole in said fourth row is axially aligned with a corresponding orifice and gain hole in said second row, said fourth row longitudinally spaced from said second row away from said first and third rows and each of said slots in said spool member has a width at one axial end substantially equal to said first aperture and a width at the opposing axial end substantially equal to the diameter of said gain holes and a length extending to said fourth row, each of said slots in commmunication with said first apertures and gain holes when said controller is in an unactuated position.

l2. A controller for a fluid pressure operated device comprising:

a servomotor;

a housing secured to said servomotor and having a generally cylindrical opening therein;

a fluid inlet, a fluid outlet and first and second selectively pressurizable ports in said housing communicating with said opening, said first and second ports being adapted to be connected in fluid communication with said fluid operated device;

a sleeve member rotatably disposed within said opena spool member disposed within said sleeve member and mounted for limited rotary movement relative to said sleeve member;

flow passage means in said spool and sleeve members operable to provide fluid communication from said inlet through said spool and sleeve members to said outlet when said controller is in a neutral position and to change fluid pressure direction through said spool member when said controller is actuated to provide fluid communication between said inlet and said servomotor and from said servomotor to one of said first and second ports;

first pressure balancing means operable to maintain said sleeve member centrally disposed within said opening;

second pressure balancing means operable to maintain said spool member centrally disposed within said sleeve member, said second pressure balancing means including said sleeve and spool members defining first and second balancing areas, said first and second balancing areas being in communication with fluid under high pressure from said inlet when said spool is displaced relative to said sleeve upon actuation of said controller; and

said first area being defined by first and second peripheral grooves in said spool member axially spaced from one another, and a plurality of axially extending, discontinuous, circumferentially spaced recesses in said spool member, each recess communicating with said first and second peripheral grooves and extending a sufficient distance to be axially aligned with said first and second ports and in communication with one of said first and second ports when said controller is actuated.

13. A controller as defined in claim 12 wherein said sleeve member has a peripheral recess axially aligned with said inlet and in fluid communication therewith and a plurality of circumferentially spaced first apertures in said recess,

said second area in said spool member defined by longitudinally extending, discontinuous balancing slots axially aligned with said apertures, said apertures being out of fluid communication with said slots when said controller is in its nonnal position and in fluid communication with said apertures when said spool is displaced relative said sleeve upon actuation of said controller.

14. A controller as defined in claim 13 wherein said 5 inlet and said fifth and sixth areas communicating with said first and second ports respectively.

I UNITED STATES ii TENT OFFICE- CERTIFICATE OF CORRECTION Patent No. 3 i Dated June 25 1974 Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below;

Column "line 23, should read pump Column 11, lines 30, 33, 37, and 53, "16", each occurrence, shoul d read 142 Signed an d sealed this 1st day of October 1974.

" (SEA Attest:

McCOY M. GIBSON JR; C. MARSHALL DANN Attesting Officer. Commissioner of Patents USCOMM-DC 6037 6-P69 FORM PO-1050 (10 69) u 5 GOVERNMENT PRINTING orncz: 930 

1. A controller operatively connected to a servomotor for actuating a fluid pressure operated device, said controller comprising valve structure including a primary movable valve element and a cooperating movable follow-up valve element; means for connecting said primary valve element to a control element for common movements therewith; said fluid servomotor including a rotary member coupled to said follow-up element for imparting follow-up movements thereto responsive to rotation of said rotary member; said valve structure defining, an inlet for connection to a source of fluid under pressure and an outlet for return of fluid to said source, a pair of fluid ports for connection to a fluid pressure operated device, and fluid passages communicating with said servomotor; said valve elements each having valve passages which cooperate to direct flow of fluid from said inlet through said servomotor to one of said ports and to direct flow of fluid from the other of said ports to said outlet responsive to movement of said primary valve element in one direction away from a neutral position relative to said follow-up valve element; movement of said primary valve element in the opposite direction from said neutral position causing said valve element passages to be disposed to direct flow of fluid from said inlet through said servomotor to the other of said ports and to direct flow of fluid from said one of the ports to said outlet; the improvement comprising: said follow-up valve element having at least a first row of a plurality of circumferentially spaced apertures and at least a second row of circumferentially spaced orifices longitudinally displaced from said first row, said orifices circumferentially oriented with respect to said apertures so that one orifice is disposed above and below each first aperture a predetermined distance, and said primary valve element having a plurality of circumferentially spaced slots of number equal to said apertures, each slot axially extending a distance at least equal to the distance from said first row to said second row, said apertures and said slots in communication with one another when said controller is unactuated.
 2. A modulating controller for controlling fluid flow to a fluid pressure operated device, said controller comprising: a casing having a cavity therein, an inlet extending into said cavity and first and second outlets extending from said cavity; first and second valve members disposed in said cavity, said first and second valve members being relatively movable between a neutral and an actuated position; said first and second valve members defining a first flow area through said valve members for providing a fluid flow path between said inlet and said first outlet when said valve members are in said neutral position; said first and second members defining a second fluid flow area through said valve members for providing a second fluid flow path between said inlet and said second outlet when said valve members are in said actuated position, said first flow area being decreased A predetermined amount in said actuated position; and a third flow area through said valve members, said third flow area being effective to modify the effective area of said first flow area during relative movement of said members between said neutral and actuated positions, said first and second valve members being sleeve and spool members respectively; said sleeve member having a plurality of first apertures circumferentially spaced thereabout, said spool member having a like plurality of circumferentially spaced slots extending therethrough; said first apertures being aligned with said slots to define first flow area, said apertures being movable out of registry with said slots to define said decreased first flow area; and said third flow area being defined by a plurality of second aperatures in said sleeve member, said second aperatures being spaced circumferentially about said sleeve member a predetermined distance on each side of at least some of said first apertures; said first apertures including a first plurality of generally circular apertures and a second plurality of larger charging apertures interspersed among said circular apertures, and said second apertures including a plurality of augmenting orifices; and said slots including a plurality of longitudinally extending slots equal in number to said first plurality and having a width at one end approximately equal to the size of said augmenting orifices and a width at the other end approximately equal to the size of said first apertures and a plurality of charging slots equal in number to said second plurality and having a width approximately equal to that of said charging apertures.
 3. A controller operatively connected to a servomotor for actuating a fluid pressure device comprising: a casing having an opening therein and at least an inlet and outlet port communicating with said opening; a hollow sleeve member rotatably disposed within said opening; a hollow spool member rotatably disposed within said sleeve member; passage means in said sleeve and spool member to direct fluid into said servomotor when said controller is actuated; control means in said spool and sleeve members to direct fluid pressure from said inlet through said spool to said outlet when said controller is in a neutral position and to change fluid pressure direction through said spool member when said controller is actuated; said control means further including said sleeve member having at least a first row of a plurality of circumferentially spaced first apertures and at least a second row of circumferentially spaced orifices longitudinally displaced from said first row, said orifices circumferentially orientated with respect to said apertures so that an orifice is disposed above and below each first aperture a predetermined distance, and said spool member having a plurality of circumferentially spaced slots of a number equal to said first apertures and in circumferentially aligned relationship with said first apertures, each of said slots axially extending a distance at least equal to the distance from said first row to said second row, said first apertures and slots in alignment with one another when said controller is in a neutral position.
 4. A controller as defined in claim 3 wherein said predetermined distance is sufficient to communicate an increasing area of said orifices with said slots after said first apertures have rotated a portion of their area out of communication with said slots as said spool and valve members rotate relative to each other.
 5. A controller as defined in claim 4 wherein said portion of said first apertures rotated out of communication with said first slots is approximately one-half the area of said first apertures before said increasing area of said orifices begins to compensate for loss of additional area of said first apertures as said first apertures continue to move out of communication with said slots.
 6. A controller as defined in claim 3 wherein said passage means includes at least first and second axially spaced peripheral pressure balancing grooves in the exterior surface of said spool member for receiving pressure when said controller is actuated to maintain said spool member centered within said sleeve member.
 7. A controller as defined in claim 6 further including a plurality of axially-extending, discontinuous grooves in the exterior surface of said spool member interspersed between said first slots and in at least partial communication with at least some of said first apertures when said controller is actuated.
 8. A controller as defined in claim 3 wherein said sleeve member has a plurality of gain holes interspersed between said orifices and circumferentially spaced and orientated to be axially aligned with said first apertures.
 9. A controller as defined in claim 8 wherein each gain hole and each orifice have substantially equal areas.
 10. A controller as defined in claim 9 wherein said sleeve member has a third row of first apertures of like number of said apertures in said first row, said apertures in said third row circumferentially orientated with respect to said first apertures in said first row to be axially aligned therewith, said third row longitudinally spaced from said first row in a direction away from said second row of orifices, and said first slots in said spool member extending to said third row.
 11. A controller as defined in claim 10 wherein said sleeve member has a fourth row of said orifices and said gain holes circumferentially spaced and aligned so that each orifice and gain hole in said fourth row is axially aligned with a corresponding orifice and gain hole in said second row, said fourth row longitudinally spaced from said second row away from said first and third rows and each of said slots in said spool member has a width at one axial end substantially equal to said first aperture and a width at the opposing axial end substantially equal to the diameter of said gain holes and a length extending to said fourth row, each of said slots in commmunication with said first apertures and gain holes when said controller is in an unactuated position.
 12. A controller for a fluid pressure operated device comprising: a servomotor; a housing secured to said servomotor and having a generally cylindrical opening therein; a fluid inlet, a fluid outlet and first and second selectively pressurizable ports in said housing communicating with said opening, said first and second ports being adapted to be connected in fluid communication with said fluid operated device; a sleeve member rotatably disposed within said opening; a spool member disposed within said sleeve member and mounted for limited rotary movement relative to said sleeve member; flow passage means in said spool and sleeve members operable to provide fluid communication from said inlet through said spool and sleeve members to said outlet when said controller is in a neutral position and to change fluid pressure direction through said spool member when said controller is actuated to provide fluid communication between said inlet and said servomotor and from said servomotor to one of said first and second ports; first pressure balancing means operable to maintain said sleeve member centrally disposed within said opening; second pressure balancing means operable to maintain said spool member centrally disposed within said sleeve member, said second pressure balancing means including said sleeve and spool members defining first and second balancing areas, said first and second balancing areas being in communication with fluid under high pressure from said inlet when said spool is displaced relative to said sleeve upon actuation of said controller; and said first area being defined by first and second peripheral grooves in said spool member axially spaced from one another, and a plurality of axially extending, discontinuous, circumferentially spaced recesses in said spool member, each recess communicating with said first and second peripheral grooves and extending a sufficient distance to be axially aligned with said first and second ports and in communication with one of said first and second ports when said controller is actuated.
 13. A controller as defined in claim 12 wherein said sleeve member has a peripheral recess axially aligned with said inlet and in fluid communication therewith and a plurality of circumferentially spaced first apertures in said recess, said second area in said spool member defined by longitudinally extending, discontinuous balancing slots axially aligned with said apertures, said apertures being out of fluid communication with said slots when said controller is in its normal position and in fluid communication with said apertures when said spool is displaced relative said sleeve upon actuation of said controller.
 14. A controller as defined in claim 13 wherein said first balancing means includes said sleeve member and said opening in said housing defining third, fourth, and fifth areas, said fourth area communicating with said inlet and said fifth and sixth areas communicating with said first and second ports respectively. 